This invention relates to suspension systems for sliding doors and particularly to suspension systems for sliding doors that are used in opening and closing doorways that provide ingress and egress from refrigerated spaces.
Today most commercial kitchens, restaurants and supermarkets use swing doors to close and open space access doorways rather than sliding doors. This is primarily due to their lower cost. Swing doors however are ill suited for use in refrigerated spaces such as walk-in coolers since they must swing freely and thus have clearance with the doorway bounding jamb or wall. Such clearance of course permits air to flow between the refrigerated space and ambience beneath the door even though it is closed. Swing doors also require substantial swing space on each side of the wall. In effect this prevents the spaces along the walls from being used as corridors. They also pose the risk of striking people accidently when doors suddenly swing open. Conversely, sliding door systems have been devised that can seal a doorway. These systems have sealing gaskets either on the door jamb or the door. The sliding doors are suspended by systems that have been quite costly and complex. This complexity and cost has been driven by the need for the door to travel laterally over the doorway and yet towards and away from it as it is brought into sealing engagement with the door jamb gaskets.
Their suspension systems have included ramps which drive the door towards and away from the doorway and adjacent wall in sealing it. They have also included floor mounted guides which typically have had to be mounted atop or inset in concrete. These have been obstacles that have been hazardous to kitchen workers who often carry heavily loaded trays through the doorway. Floor mounted tracks also collect dirt and grime which is unsanitary. Their trolley systems have been complex with numerous parts as shown, for example, in U.S. Pat. No. 4,651,469. This type system is prevalent in Europe where it is known as the Fermod system. Swing doors, especially in smaller man access sizes, cannot readily be replaced with them, or retrofitted, because of their high cost, complexity and need for floor mounted guides and tracks. With larger sizes the high cost of conventional sliding doors is simply accepted as a necessity since a swing door could take up a whole room. They also require auxiliary jambs or sub-frames to support the weight of their suspension system. They also typically have a bulky industrial appearance.
Accordingly, it is seen that a need exists for a sliding door suspension system of simpler and less expensive structure that can be used effectively in opening and sealing a doorway such as one to a refrigerated space. It is to the provision of such that the present invention is primarily directed.
In a preferred form of the invention, a suspension system is provided for a sliding door that closes a doorway in a wall that is bounded by sealing gaskets. It is of relatively simple and light weight construction so that it can be mounted directly to the wall without the need for a sub-frame. The suspension system has an upper support rail from which the door is suspended by hangers and a lower guide rail along which the door is guided. The two rails are spaced from the wall at distances to have the door slide at a tilted angle over and out of contact with the sealing gaskets except at a doorway closed, sealing position where a spring biases the door firmly against the gaskets. By attaching the hangers inboard of the center of mass of the door, the weight of the door assists in effecting a good seal.